The invention relates to apparatus for picture processing comprising an input for receiving digitized values of picture points situated within a predetermined matrix area of 2.sup.N .times. 2.sup.N points within said picture according to a predetermined sequence among said points.
Certain methods for picture processing have been described in a paper by P. A. Wintz, Transform Picture Coding, Proc. IEEE, 60 (7207); 809-820. Several possibilities described therein include, among others use of Fourier-transforms and Hadamard transforms. Such methods for picture transform are used for compressing the picture energy to a restricted area of the picture matrix. In unprocessed pictures this energy is spread out quasi-statistically over the whole picture. By means of such methods the energy of the remainder of the picture is quite limited and it has been found that now the picture may be translated into a code with substantially restricted number of code elements. The data of the processed matrix may then be applied to a quantizing member where by code values below a predetermined critical value are suppressed so that an appreciable reduction of redundancy and of irrelevant information is effected. A processed picture may thus be stored or transmitted over a data device having a restricted capacity. The amount of the reduction thus reached depends on the specific transforms used. Known methods yield results which are quite different for different pictures and often appear to give less than optimum-results.
It is an object of the invention to provide apparatus for executing an improved transform method. Specifically, square pictures of 2.sup.N .times. 2.sup.N matrix points are considered. Notably pictures with restricted amounts of contrast are considered, such as X-ray pictures. The invention provides a substantial compression of the information contained in the picture. It is a further object of the invention to provide an apparatus which is extremely simplified in operation.